In my U.S. Pat. No. 3,571,904 issued Mar. 23, 1971 and assigned to Deutsch Fastener Corp., there is disclosed a captive screw arrangement including a screw shank and sleeve member. The sleeve member has an internal bore diameter slightly greater than the diameter of the smooth shank portion of the screw so that the sleeve can be received over the shank. After the sleeve is positioned on the shank, the protruding end of the screw is then hand-rolled with threads. These threads will have an outside diameter greater than the nominal diameter of the smooth shank portion of the screw because of the working of the metal. This outside diameter of the screw threads is greater than the internal bore diameter of the sleeve, so that the sleeve is thus held captive on the screw. The sleeve itself can then be secured in a panel opening and the screw axially moved through the sleeve to threadedly engage any appropriate cooperating member to effect a fastening.
Such captive screw arrangements are advantageous simply in avoiding the loss of screws from panels and the inconvenience of having to replace dropped or lost screws.
While my above-described captive screw has been quite successful, the design is such that the screw threads can only be applied to the screw shank after the sleeve has been positioned on the shank. The axial length of the sleeve on the shank limits the axial extent of the threads formed on the shank. As a consequence of the limited thread length, when the screw is threaded into a relatively thin cooperating member to be secured to the panel, the threads may pass entirely through the cooperating member and the smooth shank portion then be in a position within the threaded cooperating member so that the screw simply spins and while it will hold the cooperating member to the panel, there is not secured a tight engagement. Such could be overcome if the threads could be made axially longer but such is not possible without interference with the sleeve.
To overcome the foregoing problem, and also to enable the use of automatic thread rolling equipment, I have invented an improved captive screw assembly and method of making the same described and claimed in my copending United States patent application Ser. No. 92,769 filed Nov. 9, 1979. In this pending application, the threads are rolled on the smooth screw shank prior to positioning of a sleeve over the shank. The sleeve is then positioned over the shank and the end of the sleeve adjacent to the underside of the screw head is peened inwardly by an appropriate sloping undercut on the screw head to decrease the internal diameter of the sleeve at this point to a value less than the external or outside diameter of the screw threads so that the sleeve is thus held captive on the threads.
The foregoing product and method of making the same, however, does not readily admit of the use of a coil spring to bias the screw head and shank away from the sleeve so that there is lacking the convenient feature of a "pop-out" screw immediately indicating release of a cooperating member to be held by the panel.